John, if you are the John Gates I know, I'm surprised you didn't call me! But I'll share my thoughts for the benefit of others on the forum. The dust you are seeing in the inlet chute is indicative of reduced airflow -- it could be due to leakage into the bin or significant buildup of fine dust in your filter stack. To test for leakage around the bin, I suggest the use of a smoke stick that will show quickly where any leak exists (smoke will flow into the leak since this is a negative pressure area). Test not only the flex hose connections, but also the lid penetration and gasket area around the bin -- if it is a galvanized ash barrel, check the handles and any seams in the barrel itself. Any leak must be resealed using silicone caulk. To test the filter bank for dust buildup, the best method is to use a 2" WG Magnahelic gauge with one port open to the atmosphere and the second in the output side of the blower. To clean the filter, Wynne Environmental recommends using moderate pressure air from the outside. I'd suggest they be taken outdoors and blowing down the throat of the filters with a leaf blower to removed the heaviest accumulation and then using an air hose from the outside of the pleats. Wear a dust mask!
Feel free to give me a call if you need help.